High-frequency heating devices, such as microwave ovens, microwave laundry dryers etc, are directly powered by the energy source via a transformer or by using an inverter circuit. Because the magnetron is powered by high-frequency switching currents, high-frequency heating devices that are powered by using an inverter circuit, operate at a lower efficiency.
The prior art document European Patent no. EP 0279514 describes a heating device comprising a magnetron powered by an inverter. By using the transistors added to the inverter circuit, it is achieved that the anode and inverter circuits of the magnetron, and a heater that is activated as the filament is turned on, are powered by a single power source.
Another prior art document, European Patent no. EP 0493604, describes a heating device comprising a magnetron powered by an inverter. By directing the inverter circuit through a control unit, it is achieved that the frequency of the resonance circuit coincides with the frequency of the control circuit at the time of starting and that the magnetron is turned on faster.